Methods of forming LaNiO3 conductive layers, ferro-electric devices with LaNiO3 layers, and precursor formation solutions

Abstract

Methods of forming lanthanum nickel oxide (LaNiO3) layers with precursor formation solutions are disclosed, along with devices made from such solutions. Also disclosed are methods for making the formation solutions using lanthanum, nickel, and a diol. The present invention enables the manufacture of LaNiO3 layers at low cost, with good resistivity properties, and a surface morphology suitable for interfacing to a ferro-electric material.

Description

FIELD OF THE INVENTION[0001]The present invention relates to thin-film structures that comprise a ferro-electric material disposed over a non-amorphous conductive layer, and methods for making the same. The structures may comprise electrical, magnetic, electro-optic, electromagnetic, and electromechanical devices. The present invention more particularly relates to lanthanum-modified lead zirconium titanate (PLZT) disposed over metallic lanthanum nickel oxide (LaNiO3).BACKGROUND OF THE INVENTION[0002]Several types of optical communication devices comprise optical waveguides, optical modulators, and optical switching structures made of electro-optic material. A substrate optical waveguide comprises a lower cladding layer formed on the substrate, a core layer having a higher index of refraction formed over the lower cladding layer, and usually an upper cladding layer formed over the core layer. An optical modulator, or an optical switching structure, may be formed in line with the opti...

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Benefits of technology

[0007]The inventors have recognized that there is a need in the art to provide for reliable integration of crystalline ferro-electric materials onto substrates, and more particularly onto conductive layers formed on the substrates. Such integration would enable the use of vertically-oriented electrodes (as opposed to conventional top electrodes), which in turn could exploit higher E / O coefficient values in the material's tensor matrix, and also provide shorter spacing distances between the electrodes that are to generate the electric field.

[0011]The inventors have found that the complexes formed between the metal atoms and the diol compounds comprise linear chains. The linear chain structure provides for an advantageous distribution of lanthanum and nickel atoms on the substrate surface prior to the firing stage, which leads to formation of crystal grains having improved electrical conductivity. In comparison to epitaxial deposition approaches, the present invention enables a lower-cost method of making the bottom electrodes.

[0012]Accordingly, it is an object of the present invention to provide improved methods of forming non-amorphous conductive films suitable for interfacing with ferro-electric materials.

[0013]It is another object of the present invention to enable these non-amorphous conductive films to be manufactured with improved control over composition and stoichiometry.

[0014]It is another object of the present invention to enable these non-amorphous conductive films to be manufactured with reduced electrical conductivity.

[0015]It is yet another object of the present invention to enable simple and low-cost methods of constructing these non-amorphous conducting films.

Problems solved by technology

However, such single crystalline materials have relatively low responses to the applied electric field compared to other inorganic crystalline materials, such as lanthanum-modified lead zirconium titanate (PLZT).

But such crystalline materials cannot be easily formed on substrate carriers, and must be grown on top of a base crystalline substrate in order to cause the material to form a crystalline structure.

This precludes using the crystalline materials in small-scale modulators and switching devices that have vertically oriented electrodes (top and bottom electrodes) since the material cannot be grown over the bottom electrode.

Thus, the potential of using inorganic crystalline materials in these devices cannot be realized.

However, this approach is not currently able to construct small-sized electro-optic switches and modulators (less than 10 μm in thickness and width), and is not practical for large-scale integration of electro-optic devices.

This large effective distance also increases the amount of voltage needed.

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